The present invention relates to an exposure time control device .[.in.]. .Iadd.for .Iaddend.a "through the lens" type single reflex camera. In a single reflex camera it is impossible to .[.do photometry while in.]. .Iadd.take a photometric measurement during an .Iaddend.exposure, so that the photometric value prior to exposure is .[.memorized.]. .Iadd.stored .Iaddend.by a .[.memory condenser.]. .Iadd.capacitor .Iaddend.so as to control the exposure .[.through said memory.]. .Iadd.by the stored .Iaddend.voltage. However, in order to .[.memorize.]. .Iadd.store .Iaddend.a wide range of .[.the.]. object brightness .[.in the memory condenser.]. a means has been adopted for giving a logarithmic compression to the illuminance on the light receiving surface of a photoconductive element and .[.memorizing the.]. .Iadd.storing .Iaddend.a voltage .[.given said.]. .Iadd.representing that .Iaddend.logarithmic compression in the .[.memory condenser.]. .Iadd.storage capacitor.Iaddend..
And, up to the present time, when the exposure is controlled .[.through said memory voltage.]. the .[.memory.]. .Iadd.stored .Iaddend.voltage .[.given said logarithmic compression.]. is given .[.the.]. .Iadd.an .Iaddend.inverse-logarithmic conversion by a .[.logarithm elongation.]. .Iadd.conversion .Iaddend.element and the exposure control circuit is operated by the output thereof.
However, in the case .[.of that.]. .Iadd.where .Iaddend.the inverse-logarithmic conversion is .[.given by the logarithm elongation element.]. .Iadd.provided .Iaddend.the voltage variation quantity given the logarithmic compression .[.for giving.]. .Iadd.representing 1 EV of variation .Iadd.relative .Iaddend.to the exposure value .[.through the output elongated.]. is restricted by the characteristic of .[.said logarithm elongation.]. .Iadd.the conversion .Iaddend.element.[., and as the result.]. .Iadd.. Thus, .Iaddend.the voltage variation .[.quantity.]. per 1 EV .[.in progress.]. of the logarithmic compression is very small, therefore, errors are .[.easy to intervene.]. .Iadd.generated.Iaddend., resulting in .[.dropping remarkably.]. .Iadd.a degradation of .Iaddend.the precision in .[.progress of the logarithm elongation.]. .Iadd.the conversion process.Iaddend..